Semiconductor packages have become more sophisticated over the last decade due to the trend of packaging multiple chips on a single substrate. Semiconductor packages which contain multiple chips or cores are commonly referred to as multi-chip modules (MCM); a series of MCM's are often mounted to a motherboard within a computing system. Typically, motherboards are embedded with conductive paths and traces such that the semiconductor packages can communicate with each other and with the outside world. Similarly, each semiconductor package has a conductive path which allows communication with other die within the semiconductor package.
FIG. 1 shows a prior art multi-chip package 150 featuring semiconductor package 101 mounted to a motherboard 100. Semiconductor package 101 has embedded traces 105 which enable communication between a first and second semiconductor die 102, 103. First and second semiconductor die 102, 103 have first bus terminals 107, 112 and second bus terminals 108, 113 and first and second semiconductor die 102, 103 communicate with other semiconductor die via their respective buses. First bus terminals 107, 112 and second bus terminals 108, 113 may be terminals of data and address buses, respectively.
Signal driver 110 may propagate signals to semiconductor package 101 via conductive paths, such as trace 105 and die/motherboard contact 106 to first bus terminal 107 of first semiconductor die 102. The signal continues its route from first bus terminal 107 and is further transmitted to other semiconductor die coupled to motherboard 100.
The signal bandwidth depends primarily on the processing power of the individual semiconductor die within the network of semiconductor packages. Presently, microprocessors have clocked speeds in excess of three gigahertz. Likewise, there is a need to effectively terminate these high speed signals after they have reached their final intended destination or “end agent.” Without properly terminating the signals at the end agent, the transmitted signals may interfere with subsequent propagated signals; thus, creating the need for on-die termination.
FIG. 1 further illustrates an on-die termination method of the prior art, which includes an ODT pin 115 coupled to end agent, second semiconductor die 103. ODT pin 115 terminates the propagated signal at end agent, second semiconductor die 103, while the on-die termination resistors are put in HighZ by grounding the on-die termination resistor 109 of first semiconductor die 102 as illustrated in FIG. 1.
The conventional on-die termination method confines the semiconductor die within a semiconductor package to function as either a middle agent or an end agent. This constraint limits the die within the semiconductor package to one orientation scheme, which further limits the size of each die mounted to the package substrate. In the multi-chip package illustrated in FIG. 1, only 2M cache of memory can be coupled to semiconductor die 102 and semiconductor die 103 due to the limited lateral area available on the package substrate.